Pancreatic cancer (PC) is one of the leading causes of cancer death in the United States with a median survival shorter than six months. Pancreatic cancer is very deadly, because it is resistant to conventional treatments and it rapidly disseminates to the lymphatic system and remote organs. Hence, it is important to identify novel drugs that target the underlying molecular events of PC growth and interfere with PC development by blocking cell division and selectively inducing tumor cell apoptosis. One particular gene that has gained attention in recent years due to its importance in a number of cancers is Forkhead Box M1 (FoxM1). FoxM1 is a transcription factor that regulates the expression of a number of genes that are involved in cell cycle regulation and metastasis. In our preliminary studies, we identified the antibiotic thiazole compounds Siomycin A and thiostrepton as potent inhibitors of FoxM1. The goal of this proposal is to investigate the role of FoxM1 in the development of pancreatic cancer and to determine the molecular mechanisms of action of Siomycin A/thiostrepton against FoxM1 and pancreatic cancer. In the first specific aim we will determine how Siomycin A/thiostrepton inhibit the transcriptional activity and expression of FoxM1 and we will test the hypothesis that downregulation of FoxM1 is the key event that leads to Siomycin A/thiostrepton-induced apoptosis in PC cells. To evaluate the efficacy of FoxM1 inhibitors as anticancer agents in vivo, we will use them against xenograft tumors developed in athymic mice by human pancreatic cancer cell lines, which are sensitive to thiazole antibiotics in vitro. The effect of Siomycin A/thiostrepton treatment on FoxM1 expression and growth of xenograft tumors will be examined in these mice. These data may not only help to develop new drugs against pancreatic cancer, but they will also facilitate better understanding of the role of FoxM1 in the etiology of PC. If the thiazole antibiotics have low toxicity and lead to pancreatic tumor regression in mice, we will conclude that these compounds may have a potential for further clinical development against pancreatic cancer. PUBLIC HEALTH RELEVANCE: Pancreatic cancer is one of the leading causes of cancer death in the United States with a median survival shorter than six months. Pancreatic cancer is very deadly, because it is resistant to conventional treatments and it rapidly disseminates to the lymphatic system and remote organs. Therefore, it is important to identify novel targets for cancer therapy that will help to interfere with development of pancreatic cancer by blocking cell division and selectively inducing tumor cell apoptosis. One particular gene that has gained attention in recent years due to its overexpression in a number of cancers is Forkhead Box M1 (FoxM1). FoxM1 is a transcription factor that regulates the expression of a number of genes that are involved in cell proliferation and metastasis. In our preliminary studies, we identified the antibiotic thiazole compounds Siomycin A and thiostrepton as potent inhibitors of FoxM1. The goal of this proposal is to investigate the role of FoxM1 in the development of pancreatic cancer and to determine if Siomycin A/thiostrepton will be able to inhibit growth of pancreatic tumors in vitro and vivo. These data may not only help to develop new drugs against pancreatic cancer, but they will also facilitate better understanding of the role of FoxM1 in the etiology of pancreatic cancer.